1. Field of the Invention
The present invention relates to a sputtering apparatus used for producing semiconductor devices, and more particularly, to a sputtering apparatus capable of forming a film on a single wafer under two or more kinds of conditions.
2. Description of the Related Art
In the manufacture of semiconductor devices, the trend toward increasing diameter of a silicon wafer is growing so as to enlarge a region for fabricating a chip. By increasing the diameter of a silicon wafer, it is possible to remarkably reduce a per-unit price of a chip. However, a per-unit price of a silicon wafer having large diameter is still high, and there is a drawback that the cost is excessively high to research and develop using a large diameter wafer.
For example, in a manufacturing process of semiconductor devices, a sputtering apparatus is used for forming various films on a substrate. FIG. 1 is a sectional view showing a conventional sputtering apparatus. This sputtering apparatus includes a cylindrical chamber 49, which is provided at its bottom with an Ar gas introducing port 47 and an exhaust port 48 for introducing gas and exhausting air, respectively. A wafer holder 50 for holding a silicon wafer 45 is disposed on a bottom wall within the chamber 49. A target electrode 41 is supported by the chamber 49 at its upper portion through an insulator 52. A high-voltage power source 43 is connected to the target electrode 41. A magnet 51 is built in the disk-like target electrode 41 so as to adjust plasma by magnetic field by the magnet 51. The target electrode 41 is formed hollow for allowing coolant 46 to flow through the target electrode 41 to cool the latter. A cylindrical shield plate 44 is supported by the upper portion of the chamber 49 such as to surround the target electrode 41, a target material 42 and the silicon wafer 45.
In the conventional sputtering apparatus constituted as described above, the Ar gas is introduced into the chamber 49 from the gas introducing port 47 while exhausting air from the sputtering chamber 49 through the exhaust port 48, thereby bringing an atmosphere in the chamber 49 into an Ar gas atmosphere of predetermined pressure. Then, if negative voltage is applied to the target electrode 41 from the high-voltage power source 43, the target material 42 is negatively charged so that Ar.sup.+ ion collides against the target material 42. Sputter atoms are released from the target material 42 due to energy caused by the collision of the Ar.sup.+ ion. When the sputter atoms reach the wafer 45 or the shield plate 44 located at the counter electrode, the sputter atoms lose energy, and a film is formed on the wafer 41 and the shield plate 44.
In the process of research and development, various films are formed on a silicon wafer by changing conditions such as sputtering power and sputtering time, and the wafer is evaluated. In this case, if the conventional sputtering apparatus is used, it is necessary to use one wafer for each of the various film formation conditions. Therefore, if the research and the development are to be carried out by the sputtering apparatus using the conventional large-diameter wafer, there is a drawback that it is expensive.
Meanwhile, as a technique for preventing a surface of the target from being broken during the sputtering, there is proposed a target structure in which film formation material is divided into a plurality of pieces, and these pieces are arranged on a flat plate as a single film formation material (Japanese Patent Application Laid-open No. 5-263234). However, this prior art can not remove the waste caused when the large-diameter wafer is used in the process of experiment and research either.